This RFC allows bpf socket filter programs to look into complete skb i.e. linear and non-linear part of skb. (patch1)
For a proof of concept I'm using RDS sample program that uses bpf socket filter and inspect skb packet data from linear and non-linear part e.g. skb frags. (patch 2 and 3) I'm sharing this RFC to get some feedback on direction. Details: patch1 adds new bpf helper function and needed infrastructure so that socket(sk) filter based eBPF program can retrieve non-linear part of skb (e.g. skb frags) unlike current socket filter that only deals with linear skb. This patch adds very basic functionality and for now allow socket filter programs to only read packet data (from linear and non-linear part of) skb. The idea behind this patch is to add eBPF helper that allow socket filter based ebpf program to walk through the skb frag using bpf tail call. This way ebpf program can do deep packet inspection (i.e. allows to look into headers as well as payload). patch2 adds sample ebpf socket filter program that uses rds socket. The sample program opens an rds socket, attach ebpf program to rds socket and uses bpf helper added in patch 1 to look into skb. For a test, current ebpf program only prints first few bytes from skb->data and skb frags. patch3 allows rds_recv_incoming to invoke bpf socket filter program if any program is attached to rds socket. FYI, I'm also working on a follow-up patchset that deals with *struct scatterlist* to allow RDS filtering for IB/RDMA use cases that do not have an sk_buff. Thanks. -Tushar Tushar Dave (3): ebpf: add next_skb_frag bpf helper for sk filter samples/bpf: add sample RDS program rds: invoke sk filter attached to rds socket include/linux/filter.h | 2 + include/uapi/linux/bpf.h | 10 +- net/core/filter.c | 44 ++++- net/rds/recv.c | 17 ++ samples/bpf/Makefile | 3 + samples/bpf/rds_skb_kern.c | 87 +++++++++ samples/bpf/rds_skb_user.c | 311 ++++++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 10 +- tools/testing/selftests/bpf/bpf_helpers.h | 2 + 9 files changed, 482 insertions(+), 4 deletions(-) create mode 100644 samples/bpf/rds_skb_kern.c create mode 100644 samples/bpf/rds_skb_user.c -- 1.8.3.1
